A storage type hot-water supply system having a heating function and a hot-water supply function is conventionally known. For example, JP 2004-183934 A describes a storage type hot-water supply system provided with a tank for storing hot water for hot-water supply, and a pipe for heating and a pipe for hot-water supply that are wound around the outer peripheral surface of the tank in contact with each other. A heat medium (generally water) for heating is heated by the heat exchange between the heat medium flowing through the pipe for heating and hot water flowing through the pipe for hot-water supply. Indoor heating can be performed using the heated heat medium. Basically, a heat pump is used only for boiling water for hot-water supply.
On the other hand, for example in Europe, a storage type hot-water supply system with a configuration indicated in FIG. 11 is widely used. The storage type hot-water supply system indicated in FIG. 11 is provided with a first tank 300 for storing hot water for heating, a second tank 302 for storing hot water for hot-water supply, and a heater 308 disposed inside the first tank 300. The second tank 302 is mounted to the first tank 300 with a part thereof being exposed to the inside of the first tank 300. The water of the second tank 302 is heated by the heat exchange between the hot water of the first tank 300 and the water of the second tank 302. The hot water of the second tank 302 is supplied to a hot-water tap 304, and the hot water of the first tank 300 is supplied to a radiator 306 for heating.
According to the system indicated in FIG. 11, the hot water of the first tank 300 can be supplied directly to the radiator 306 in a large amount. It is therefore easier to deal with a heavy heating load, compared to the system of JP 2004-183934 A having only one tank. Although the volume of the second tank 302 is less than that of the first tank 300, in the region where people are not accustomed to using a large amount of hot water in a short time, such as filling the bathtub with hot water, there is little problem of lack of hot water even with such a configuration. In recent years, a heat pump began to be employed instead of the heater 308 for improving energy consumption efficiency.
However, the system indicated FIG. 11 still has a problem in that, in cold areas where the variation of the load and the amount of the load are significant, a load exceeding the heating performance of the heater or the heat pump may occur, so that a sufficient heating effect cannot be achieved. Such a problem particularly is likely to occur in a time period in which rapid heating is required (for example, in the morning and evening).
As a countermeasure to such a sudden load increase, the volume of the tank for storing hot water for heating is increased, the set temperature of the hot water to be stored in the tank is adjusted (water temperature is set higher), the heating performance of the heat pump is improved, and an auxiliary heater is used, for example. However, the increase in the volume of the tank causes an increase in the amount of the heat radiation from the tank to the outside, so that the energy consumption efficiency is decreased. There also is a limit in setting the temperature of the hot water to be stored in the tank higher. The improvement of the heating performance of the heat pump involves an inevitable rise in the cost. Although an auxiliary heater is preferably provided in view of enhancing the maximum heating performance of the system, the more the system is dependent on the auxiliary heater, the more the advantages of the heat pump having an excellent energy consumption efficiency are reduced.
In view of such circumstances, it is an object of the present invention to provide a hot-water supply system that is comparable to conventional systems in the energy consumption efficiency and cost and is also capable of dealing with a sudden load increase.